Cyclooxygenase and PC12 Cells Following differentiation with NGF, PC 12 cells have been shown to express elevated levels of prostaglandins. Prostaglandins arise from arachadonic acid metabolism through the activity of cyclooxygenase (COX) which exists as two isoforms. COX-1 is typically found to be constituitively expressed in a variety of cell types, whereas COX-2 behaves similarly to other immediate early genes in that it is rapidly and transiently induced. We set out to determine which isoform of COX is induced by NGF in PC 12 cells and to begin to understand the mechanism of this induction. We found that NGF induces COX-1 protein throughout the cytoplasm and neurites of PCX cells, a subcloned PC12 line. COX-1 was induced by NGF in a dose-dependent fashion, reaching peak levels between 24-48h and remaining elevated for as long as 1Od. This induction was inhibited by neutralizing antibodies to NGF. Moreover, bFGF but not EGF caused a similar Induction of COX-1 protein, suggesting a potential mechanism for this phenotypic change. Similarly, mRNA levels for COX-1 peaked between 6 and 12h and remained above basal levels for at least 48h in response to NGF. Cyclohexamide inhibited this message increase. COX-1 activity peaked at 2 days with a 15-fold induction over non-treated cells and this increase was inhibited by indomethicin with an IC50 similar to previously reported values for COX-1. Currently, our aim is to determine whether NGF induction of COX-1 in PCX cells is via Ras activation or through some other mechanism. A second area of interest is the functional role that prostanoids play in PC12 differentiation by NGF. Keywords: COX-I, NSAIDs, PC12 cells, Ras, sensory neurons